1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device including a circuit including a transistor and a test method of the semiconductor device. The present invention relates to an electronic device equipped with a display device using an active element which is, for example, an active element including an oxide semiconductor, as a semiconductor element.
In this specification, a semiconductor device generally means any device which can function by utilizing semiconductor characteristics; an electrooptic device, a semiconductor circuit, and an electronic device are all included in the category of the semiconductor device.
2. Description of the Related Art
Although transistors using amorphous silicon have been used for conventional display devices typified by liquid crystal televisions, an oxide semiconductor has attracted attention as a material which replaces a silicon semiconductor. For example, an active matrix display device in which an amorphous oxide including In, Ga, and Zn is used for an active layer of a transistor and the electron carrier concentration of the amorphous oxide is lower than 1018/cm3 is disclosed (see Patent Document 1).
However, there have been some problems in such a transistor using an oxide semiconductor. One of the problems is the stability of the characteristics; it has been pointed out that the electric characteristics of the transistor are changed by irradiation with visible light or ultraviolet light.